Valves suitable for use in instruments and instrumentation systems are well known. One particularly useful type of valve for these systems comprises a ball valve. Generally, a ball valve includes a chamber or body with an internal valve chamber with inlet and outlet passages.
A ball valve member is disposed within the internal valve chamber. The ball valve member comprises a stainless steel ball positioned centrally within the chamber and a cylindrical valve stem which extends from the ball axially through the chamber to a location outside the body. Packing material surrounds the ball and stem and fills the voids between the ball and the chamber, except for passages which extend from the inlet and outlet passages in the body to the ball. A handle attached to the operating stem allows the ball to be rotated, thereby selectively aligning passages in the ball with the inlet and outlet passages in the body. The ball valve can be a two-way valve with a single inlet and single outlet passage, or a three-way valve with a single inlet and a pair of outlet passages, or a pair of inlet passages and one outlet passage, depending on what the particular application requires.
A needle valve is a type of valve in which a valve member, or a needle, is mounted within a valve body for axial movement along a valve closure axis into, and out of, a valve seat cavity. Flow passages, opening into the valve seat cavity, are formed in the valve body so that the valve can be closed by inserting the needle into the valve seat cavity and opened by withdrawing the needle from the valve seat cavity while providing more accurate control for the passage of the fluid to the outlet.
As illustrated in FIG. 1, a ball valve 2 and a needle valve 4 can be combined in a parallel manner to control the passage of a fluid within pipeline 6. These two kinds of valves are usually installed parallel to each other in order to exploit the advantages of each one of the valves for various needs. This solution which is illustrated in FIG. 1 suffers from different disadvantages such as: variety of components, many potential leakage points, cost-effectiveness, elevated labor costs, elevated chances for damages, and other disadvantages.
Therefore, there is a long felt need to develop a compact valve which will encapsulate both a ball valve and a needle valve in a single construction. The present invention is intended to comply with this requirement.
The known in the art valve suffer from the following disadvantages:    1. Ball valves do not have a regulation mode which is between a fully opened mode and a fully closed mode. The known in the art ball valves are designed to operate only for shut-off control.    2. Metering valves are designed to regulate flow in a precise manner, and are not suitable for shut-off control.